The present invention relates to an engine speed control device and method.
In particular, the present invention may be used to advantage, though not exclusively, for controlling the speed of a vehicle engine, to which the following description refers purely by way of example.
As is known, in the automotive industry, ensuring maximum driving comfort of a vehicle during transient engine speed states is one of the hardest things to achieve.
This is particularly so in certain engine operating conditions, as, for example, when braking the vehicle running in gear at minimum engine speed, which produces increasingly severe shaking, and hence discomfort to the driver and passengers, as a result of the central control unit counteracting the brake-produced reduction in engine speed to keep the engine at minimum speed.
Other operating conditions resulting in driver and passenger discomfort in the form of jolting are when accelerating sharply after releasing the brake, or when the central control unit gradually brings the engine down to minimum speed when the accelerator pedal is released.
More specifically, when the accelerator pedal is released, engine speed normally tends to undershoot, i.e. fall slightly below minimum, only to return to minimum immediately after, thus resulting in jolting of the driver and passengers.
The engine speed control algorithms employed so far by central control units for the purpose of improving driving comfort provide for PI (proportional-integral) or PID (proportional-integral-derivative) control, and, besides being generally ineffective in eliminating the above drawbacks, comprise numerous calibration parameters enabling calibration purely by trial and error. At present, in fact, control algorithms are calibrated by first performing a series of road tests to determine performance of the vehicle in the above operating conditions, and then calibrating the control algorithm parameters substantially manually, trusting in the skill of technicians with many years"" experience.
It is an object of the present invention to provide an engine speed control method and device designed to at least partly eliminate the aforementioned drawbacks.
More specifically, it is an object of the present invention to provide an engine speed control method and device which not only provide for significantly reducing driver and passenger discomfort in the above operating conditions, but which can also be calibrated by deterministic methods.
According to the present invention, there is provided an engine speed control device as claimed in claim 1.
According to the present invention, there is also provided an engine speed control method as claimed in claim 10.